1. Field of the Invention
The present invention relates to a coaxial connector that is connected to a coaxial cable at one end for external connection. More particularly, the coaxial connector is connected to a coaxial cable that is run in environments where the coaxial conncetor undergoes thermal shock and variation in temperature.
2. Description of the Prior Art
Referring now to FIG. 8, a conventional coaxial cable designed to carry high-frequency signal includes a central conductor 111. Central conductor 111 is coaxially layered with an insulated cable dielectric 112, a woven or braided outer conductor 113 and an insulating outer cladding 114 as shown. Referring now to FIG. 9, in a conventional design coaxial connector 100 is affixed to one end of the the coaxial cable and enables connection to other equipment or another coaxial cable.
Conventional coaxial connector 100 includes a central contact 101 formed by bending a conductive metal sheet. An insulating housing 103 surrounds a contact receiving hole 102 formed to receive the central contact 101. A cylindrical grounding shell 104 mounts on an outer surface of insulating housing 103.
Central contact 101 has a forward (to right-hand side in FIG. 9) portion formed as a plate-spring-like contact piece 108 and a rearward portion formed as a conductor clamping barrel 106, 108. to connect with central conductor 111. Contact receiving hole 102 extends through insulating housing 103 lengthwise and receives central conductor or switch for contact 101 during an assembly. Contact receiving hole 102 also guides a plug pin 120 of, a mating connector, into contact with contact piece 108.
Referring now to FIG. 10, an assembly sequence for connecting a coaxial cable to coaxial connector 100 is shown and described. First, a cylindrical clamp 107 is placed on coaxial cable, and then a grounding shell 104 is slid onto insulating housing 103 from behind to form a unitary structure. Next, central conductor 111 is inserted into clamping barrel 106. Central conductor 101 has a U-like cross section formed at rear end portion of central contact 101.
At same time central contact 101 is inserted into insulating housing 103, a shell connecting part 105, that extends rearwardly from grounding shell 104, is inserted between cable dielectric 112 and outer conductor 113. Therefore, outer conductor 113 and outer cladding 114 are clamped together by clamp 107 which was fitted on coaxial cable.
Since grounding shell 104 is fixed to insulating housing 103, coaxial connector 100 is mechanically connected to coaxial cable. Also, central contact 101 and grounding shell 104 are electrically connected to central conductor 111 and outer conductor 114, respectively.
When a coaxial cable connected to coaxial connector 100 above, is used in environments where wide temperature variations are encountered, central conductor 111 and cable dielectric 112 typically expand or contract relative to outer cladding 114. This movement variation is due to the fact that central conductor 111, cable dielectric 112, outer conductor 113 and outer cladding 114 have different thermal expansion coefficients.
When the expansion or contraction occurs, since outer conductor 113 and outer cladding 114 are fixed to insulating housing 103 through grounding shell 104, central contact 101, which is fixed to central conductor 111, is likely to be pulled out of insulating housing 103. A protrusion 102a is located at an intermediate portion of the central contact 101. Protrusion 102a prevents rearward movement of central contact 101 by engaging a locking stepped portion 101a protrusively provided in contact receiving hole 102. This is to prevent central conductor 111 from being pulled out of insulating housing 103 even if contraction of central conductor 111 occurs.
Conventional coaxial connector, 100 protrusion 101a is in central contact 101. Contact receiving hole 102 is provided with stepped portion 102a for engaging protrusion 101a. Stepped portion 102a is formed by cutting a U-groove 109 (see FIG. 10) lengthwise into the interior surface of contact receiving hole 102 at front end face of insulating housing 103 after it is removed from a molding die.
This structure may, due to thermal expansion or contraction, allow central contact 101 to tilt and partly enter into U-groove 109 of contact receiving hole 102. If control contact 101 is tilted, plug pin 120 will not correctly make resilient contact with contact piece 108 once inserted into contact receiving hole 102. Also, plug pin 120 must be inserted with greater force causes plastic deformation of contact piece 108.
Further, since U-groove 109 creates a detrimental air gap at an asymmetrical position about central contact 101, distortion will occur which will not match characteristic impedance of coaxial cable, this distortion will degrade high-frequency signal transmission characteristic.
Moreover, it is necessary to insert central contact 101 into contact receiving hole 102 while bringing protrusion 101a into engagement with stepped portion 102a, this impairs efficiency of assembling.
Also, since central contact 101 is inserted into contact receiving hole 102 until protrusion 101a goes beyond stepped portion 102a, they are always separated by a slight gap xcex4 as illustrated in FIG. 9. Inevitably, after assembly, central contact 101 moves as central conductor 111 contracts.
Thus, there is still a need in art to devise a coaxially connector that will hold central contact in place regardless of thermal conditions and expansion and contraction caused therefrom.
It is an object of the present invention to provide a coaxial connector that, even if thermally shocked, securely holds the central contact in place within the insulating housing and prevents breakage of the central contact.
Another object of the present invention is to provide a coaxial connector wherein, even if thermally shocked, securely retains and prevents degradation of the high-frequency transmission characteristic of the coaxial cable.
Another object of the present invention is to provide a coaxial connector that can be assembled with high efficiency.
It is the foregoing and various of drawbacks of the prior art which the present invention seeks to overcome by providing a coaxial connector that includes a central connector having a forward portion where a contact portion makes electrical contact with a central terminal of the mating connector. The central connector also has a rearward portion where a conductor connecting portion is crimped into contact with a central conductor of a coaxial cable. An insulating housing is bored lengthwise through a contact receiving hole to receive the central contact in place, and also, a grounding shell is mounted over the insulating housing and has a shell connecting portion extending from a rear end of the insulating housing. The grounding shell is crimped into contact with an outer conductor of the coaxial cable. Additionally, a marginal portion of the insulating housing around the conductor connecting portion, is thermally fusion welded to fixedly secure the central contact to the insulating housing when the terminal of the central conductor is brought into contact by crimping from the outside.
The terminal of the central conductor is crimped to the marginal portion of the conductor connecting portion from the outside of the marginal portion. Thus, the crimping action makes the surface of the marginal portion uneven and the thermally fused material of the insulating housing adheres to the uneven-surfaced marginal portion of the conductor connection portion. The adhering of the fused material firmly fixs the insulating housing and the central contact to each other.
Accordingly, the central contact will not be displaced in the insulating housing by the expansion or contraction of the central conductor when the coaxial cable undergoes thermal shock.
According to another aspect of the present invention, the conductor connecting portion is a crimp barrel of U-shaped cross section in a plane perpendicular to the lengthwise direction of said insulating housing and at least one groove is cut in the outer surface of said crimp barrel.
The groove in the outer surface of the crimp barrel ensures its deformation in the direction of extension of the groove by crimpingxe2x80x94this enables the central conductor to be crimped into contact with the insulating housing with great strength.
Since the groove extends in a direction perpendicular to the lengthwise direction of the contact receiving hole, the thermally fused material of the insulating housing fills in the groove, by which the central contact is fixed more firmly.
According to still another aspect of the present invention, the shell connecting portion has engaging pieces which are bent into a cable dielectric surrounding the central conductor of the coaxial cable. This engages the shell connecting portion to the cable dielectric. Also, the outer conductor covering the shell connecting portion engages with the cable dielectric and the outer cladding of the coaxial cable rearward of the outer conductor. The outer conductor and the cable dielectric are crimped from the outside by a clamp to hold the cable dielectric as a unitary structure with the outer cladding through the shell connecting portion, the outer conductor and the clamp.
By the engagement of the engaging pieces of the shell connecting portion with the cable dielectric, the cable dielectric is fixed to the grounding shell attached to the insulating housing. Accordingly, the expansion or contraction of the cable dielectric by thermal shock is prevented by the fixed grounding shell; that is, the central conductor is free from the influence of the expansion or contraction of the cable dielectricxe2x80x94this further ensures preventing the displacement of the central contact.
The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of a specific embodiment thereof, especially when taken in conjunction with the accompanying drawings wherein like reference numerals in the various figures are utilized to designate like components, and wherein: